During the fabrication of an integrated circuit package, a die containing a plurality of circuit patterns is connected to an integrated circuit package substrate. The package substrate has a plurality of pins for connecting the circuitry to an external printed wiring board.
The most common method for forming electrical connections between the die and the package substrate is wire bonding. A plurality of bonding pads is located around the perimeter on a top surface of the die. A corresponding set of contacts is located on the package substrate. A plurality of connecting wires are bonded to connect each bonding pad to a respective contact on the package substrate, using a method such as ultrasonic bonding. Following wire bonding, the package is encapsulated and sealed.
Traditional bonding pads have the same shape as the first metal layer (M1). Typical bonding pads in the prior art have solid metal pads, in a rectangular or square configuration. In this type of pad, the bonding pad corner has a high stress concentration and often peels or lifts up during wire bonding. In addition to pad peeling, interface peeling, pad carpeting and inter-metal dielectric (IMD) cracking may occur. This has an unfavorable effect on yield.
Prior attempts to reduce the stress concentration at the corners of the bonding pad have included use of rounded corners and beveled corners that give the bonding pad an octagonal shape. Other techniques for reducing peeling have included increasing the corner adhesion by surface treatments or increasing the contact area. U.S. Pat. No. 6,313,541 is incorporated by reference herein for its teachings on a structure for reducing peeling in a bond pad through formation of dendritic sub-structures in a dielectric layer surrounding the bonding pad.
An improved bonding pad is desired.